Muffle burner

ABSTRACT

The muffle burner has a tubular member to divide the burner into two concentric air flow ducts about the fuel line. The ducts are supplied with air over separate lines from a common duct. The air flow in the line for the inner flow duct is regulated by the adjustment of the amount of air flow in the other line via the flow adjusting valve.

United States Patent 1151 3,695,817 Sharan [45] Oct. 3, 1972 MUFFLE BURNER [72] Inventor: Harendra Nath Sharan, Seuzach, [56] References Cited Swltzerland UNITED STATES PATENTS [73] Assgnee g f wmthenhu" 3,486,834 12/1969 Frey et al ..431/12 3,356,122 12/1967 Rackley et al. ..431/1s3 x [22] Filed; May 18, 1970 3,049,173 8/1962 Costello et a1 ..431/l84 [21) pp No: 38,123 3,310,096 3/1967 De L1vo1s ..43l/l78 X Related s Application Data Primary Examiner-Edward G. Favors Attorney-Kenyon & Kenyon Reilly Carr & Chapin [63] Contlnuation-m-part of Ser. No. 880,683, Nov.

28, 1969. [57] ABSTRACT 30 Foreign Applicafion p i i Data The muflle burner has a tubular member to divide the burner into two concentric air flow ducts about the May 1969 Swnzefland -17646/68 fuel line. The ducts are supplied with air over separate lines from a common duct. The air flow in the line for [52] US. Cl ..431/l78, 431/182 the inner flow duct is regulated by h adjustment f [51] Int. Cl. ..F23c 5/08 the amount of flow in the other i via the flow [58] Field ofSearch ..43l/l8l, 182, 183, 184, 185,

adjusting valve.

5 Claims, 2 Drawing Figures MUFFLE BURNER This application is a continuation-in-part application of copending application Ser. No. 880,683 filed Nov. 28, 1969.

This invention relates to a muffle burner and more particularly to a turbulence muffle burner having a central fuel supply means.

As described in the parent application, a swirl-type muffle burner is provided with a central means for supplying liquid or gaseous fuel which is surroundedby at least two concentric annular combustion air supply ducts each having disposed therein means for imparting twist to the air flowing therethrough and an adjacent refractory muffle. The construction is such that, over the entire load range, the velocity of the air leaving the innermost of the annular ducts is greater than the velocity of the airleaving the outermost of the annular ducts and the tangential velocity component of the air discharged from the innermost of the annular ductsis greater than the tangential velocity component of the air discharged from the outermost of the annularducts.

For satisfactory burner operation, it is important that the amount of air supplied to the annular duct adjacent the axis of the burner must remain substantially constant, to maintain a stable flame. In the burner particularly described in the parent application, this is achieved by an axially adjustable sleeve which alters the flow cross-section of the annular duct remote from the burner axis.

The present invention provides an improvement to the burner which enables the air supply to the annular duct adjacent the axis to be kept constant by means of a very simple and reliable construction.

Briefly, the present invention connects each of the annular ducts of a swirl-type muffle burner as described in the parent application via a branch line to a common air-supply line. In addition, the branch line which extends to the annular duct (or to one of the annular ducts) other than the innermost of the annular ducts, contains a flow adjusting means. This low adjusting means is used to regulate the flow of air through the innermost annular duct by controlling the air flow through the annular duct in which the adjusting means is mounted. That is, as the adjusting means is closed the flow of air is reduced in the annular duct housing the same while the flow of air in the innermost duct is caused to increase. I

This air distribution system has the advantage that the burner, which will normally be demountable, need have no driven parts. Another advantage is that the movable parts, i.e. the flow adjusting means, are less subjected to the action of the heat evolved in the burner, so that the burner is more reliable. The arrangement also enables the firing system to be extended in a very simple manner, since it will usually be possible for further burners to be connected to the branch lines without the necessity of extra flow adjusting means.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a horizontal sectional view through a swirl-type muffle burner according to the invention; and

FIG. 2 illustrates a similar view of a construction having three swirl-type muffle burners.

Referring to FIG. 1, a burner il has a cylindrical airdistribution box 2' subdivided by a transverse an 52 having e.g. a cylindrical portion and a radially flanged portion into two chambers 53, 54. The innermost chamber 53 opens into an inner annular duct 50 adjacent the burner axis and the other chamber 54 opens into an outer concentric annular duct 40 coaxial therewith and remote from the burner axis. The annular ducts 50, 40 each contain swirl means l1, 12, respectively,.. for imparting twist to the air flowing through the ducts. Aburner lance 4 which is supplied with fuel through a line 5 is disposed in the center of the burner l. Adjoining the annular ducts 40, 50 is a ceramics-lined muffle forming a combustion chamber 55 which discharges into a space 56 defined by walls which are lined with tubes 20 carrying a working-medium. The tubes 20 can be the preheating, evaporating or superheating surfaces of a steam generator.

Air for combustion is supplied through a duct 3 which divides into two branch lines, 57, 58; the line 57 extending into the chamber 53 of the inner annular duct 50 adjacent the burner axis via a suitable opening in the box 2' and the line 58 extending into the chamber 54 of the outer annular duct 40 remote from the burner axis via another opening in the box 2'. In order to vary the amount of air flowing to the annular duct 54 remote from the burner axis, a flow adjusting means 59, such as a flap valve, is mounted in the other annular duct 52. In addition, a pressure senser in the form of a Pitot tube 60 is mounted with one end extending into the branch line 57 while the other end is connected to a diaphragm chamber 61. A second pressure senser in the form of a tube 62 is disposed with one end opening into the space 56 downstream of the burner 1, while the other end is connected to a diaphragm chamber 63. The diaphragms (not shown) in the chambers 61, 63 operate a slide valve 64 disposed therebetween to form a difference-forming member which is connected by pressure medium lines 65, 66 to opposite sides of a servomotor 67 with a piston which acts on a linkage 68 to actuate the flow adjusting means 59. As the flow adjusting means 59 is adjusted by the servomotor 67, the flow of air through the branch line 58 is controlled. This, in turn, causes the air flow in the other branch line 57 to be regulated in an algebraically opposite sense.

In order to regulate the fuel feed, the fuel line 5 has a measuring orifice plate 70 therein which is connected via a differential pressure measuring member 71 to a control unit 72 which provides an output signal which acts on a servomotor 73 to actuate a fuel-flow adjusting valve 74 in the line 5. The air duct 3 has a corresponding control circuit for regulating the total amount of air supplied to the burner 1. This control circuit includes a constriction 75 in the duct 3, a differential pressure measuring member 76 which measures the difference in pressure between the constriction 75 and an upstream point to emit a corresponding signal to a control unit 77 which provides an output signal which acts on a servomotor 78 and an adjusting flap 79 controlled by the servomotor 78 which alters the total flow of air.

Each of the two control units 72, 77 is supplied with a r quantity of fuel and air being regulated by means of the described control circuits 70-74; 75-79. The total amount of air is so distributed between the branch lines 57, 58 that a substantially constant amount of air is fed to the inner annular duct 50 adjacent the axis, while the remaining quantity of air flows into the outer annular duct 40 remote from the axis. In order to maintain the amount of air flowing through the branch line 57 constant, the pressures in the branch line 57 and in the space 56 are measured by the pressure sensers60, 62. The difference between these pressures is formed by the diaphragms 61 and 63, and-if such difference in pressure exceeds an upper or lower limit, the flowadjustingmeans 59 is moved. If the difference in pressure is excessive, i.e., if too much air flows through the branch line 57, the slide valve 64 is moved to the left, as viewed, and pressure medium is supplied via line 65 to the right-hand side of the servo piston, resulting in a displacement of the adjusting means 59 which increases the flow cross-section in the branch line 58, so that a larger proportion of the air supplied through the duct 3 reaches the annular duct 40 remote from the axis. The proportion of air flowing through the branch line 57 is reduced accordingly. In this way, therefore, the amount of air flowing to the annular duct 50 adjacent the burner axis is regulated by the adjustment of the amount of air flowing to the annular duct 40 remote from the axis.

In an alternative construction, the sensers 60, 62 can be replaced by an orifice plate (not shown) in the branch line 57 and a differential pressure measuring member (not shown) operatively connected to the flow adjusting means 59.

Referring to FIG. 2, instead of using only one swirltype muffle burner, a number of muffle burners whose combustion chambers all discharge into the space 56 can be connected in parallel to the branch lines 57, 58 downstream of the pressure senser 60 and the flow adjusting means 59. Each of these muffle burners l are constructed as above described and need not be further described.

What is claimed is: a

1. In combination with a steam generator having a space therein;

a plurality of muffle burners communicating with said space, each burner having a means for supplying fuel and at least two concentric annular ducts disposed about said means for supplying combustion air;

swirl means in each of said annular ducts for imparting twist to the air flowing axially through each;

a common air supply line;

a pair of branch lines extending from said air supply line to each muffle burner, one of said branch lines connected in common to the inner ducts of each burner and the other of said branch lines connected in common to the outer ducts of each burner;

measuring means connected between said space and said one branch line for measuring the difference in pressure therebetween;

a flow adjusting means mounted in said other branch line upstream of said muffle burners for controlling the flow of air therethrough and to regulate the flow of air through said one branch line;

m ai ns connected between said measuring means and said flow adjusting means for actuating said flow adjusting means in response to said measuring means measuring predetermined differences in pressure between said space and said one branch line.

2. The combination as set forth in claim 1 wherein said means between said measuring means and said flow adjusting means actuates said flow adjusting means to maintain a constant pressure in said one branch line.

3. The combination as set forth in claim 1 which further includes a control circuit connected to said air supply line for regulating the total amount of air supplied to said burners, said circuit including a differential pressure measuring means for measuring the difference in pressure between a predetermined point in said air supply line and a point upstream thereof, a control means connected to said differential pressure measuring means to receive an actuating signal therefrom in response to measured differential pressure, and a flow adjusting means in said air supply duct connected to said control means to be adjusted thereby in response to said signal.

4. The combination as set forth in claim 1 wherein said flow adjusting means includes a constriction in said air supply line, a differential pressure measuring means for measuring the difference in pressure between said constriction and a spaced apart point in said air supply line, and a control unit connected to said pressure measuring means to receive a signal therefrom corresponding to a measured difference in pressure and connected to said adjusting flap to alter the position of said flap in response to a received signal from said pressure measuring means.

5. The combination as set forth in claim 1 which further includes a control circuit connected to said air supply line for regulating the total amount of air supplied to said burners, said circuit including an adjusting flap in said air supply line and means connected to said flap to adjust said flap. 

1. In combination with a steam generator having a space therein; a plurality of muffle burners communicating with said space, each burner having a means for supplying fuel and at least two concentric annular ducts disposed about said means for supplying combustion air; swirl means in each of said annular ducts for imparting twist to the air flowing axially through each; a common air supply line; a pair of branch lines extending from said air supply line to each muffle burner, one of said branch lines connected in common to the inner ducts of each burner and the other of said branch lines connected in common to the outer ducts of each burner; measuring means connected between said space and said one branch line for measuring the difference in pressure therebetween; a flow adjusting means mounted in said other branch line upstream of said muffle burners for controlling the flow of air therethrough and to regulate the flow of air through said one branch line; and means connected between said measuring means and said flow adjusting means for actuating said flow adjusting means in response to said measuring means measuring predetermined differences in pressure between said space and said one branch line.
 2. The combination as set forth in claim 1 wherein said means between said measuring means and said flow adjusting means actuates said flow adjusting means to maintain a constant pressure in said one branch line.
 3. The combination as set forth in claim 1 which further includes a control circuit connected to said air supply line for regulating the total amount of air supplied to said burners, said circuit including a differential pressure measuring means for measuring the difference in pressure between a predetermined point in said air supply line and a point upstream thereof, a control means connected to said differential pressure measuring means to receive an actuating signal therefrom in response to measured differential pressure, and a flow adjusting means in said air supply duct connected to said control means to be adjusted theReby in response to said signal.
 4. The combination as set forth in claim 1 wherein said flow adjusting means includes a constriction in said air supply line, a differential pressure measuring means for measuring the difference in pressure between said constriction and a spaced apart point in said air supply line, and a control unit connected to said pressure measuring means to receive a signal therefrom corresponding to a measured difference in pressure and connected to said adjusting flap to alter the position of said flap in response to a received signal from said pressure measuring means.
 5. The combination as set forth in claim 1 which further includes a control circuit connected to said air supply line for regulating the total amount of air supplied to said burners, said circuit including an adjusting flap in said air supply line and means connected to said flap to adjust said flap. 